[R-390] Collins R 389 PTO

[Roy Morgan]

On Apr 30, 2009, at 3:08 PM, Jon Schlegel wrote:

> How similar is the 389 PTO to the 390 PTO?  Would it be possible to
> do some sort of mix n match?

The only similarity is the size, shape, and appearance of the PTO's,  
and possibly the supply voltages.  It is not possible to do some sort  
of mix and match.

The R-389 PTO is the only 50 turn PTO that Collins made (as far as I  
know).  It has been reported to be the most difficult to produce PTO  
they made.
It's frequency range is not the same as any other PTO (again as far as  
I know)

Cecil wrote:
"The electro-mechanical drive system goes nuts and twists the PTO  
beyond the
stops shreading the internals..."

In addition, it's possible for the *operator* to destroy the PTO.  A  
feature of the R-389 that is not at all obvious is that the main  
tuning knob is equipped with a friction clutch.  After many years of  
humidity and neglect, the clutch may well be frozen.  (It was in my  
radio.) This allows just moderate torque on the knob by an un-knowing  
operator to destroy the innards of the PTO.

Here are just a few of the things wrong with the PTO in my R-389:

- The coil form is cracked loose from the mounting plate, cracked  
clear through part way through the windings and twisted out of position
- The core is cracked and there are small pieces missing
- The corrector stack follower mechanism is bent 90 degrees from normal
- The corrector follower mechanism is torn loose from the tuning rod  
assembly
- The corrector stack mounting frame is bent
- The tuning rod is bent.

It looks like for the uncertain future, if I want to listen to VLF,  
I'll turn to an RAK, an RBL, or the CEI (Watkins Johnson)  VLF 354..

Roy

Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073